Electrolytes for high-voltage cathode materials and other applications

ABSTRACT

The present invention generally relates to electrolytes for use in various electrochemical devices. In some cases, the electrolytes are relatively safe to use; for example, the electrolytes may be resistant to overheating, catching on fire, burning, exploding, etc. In some embodiments, such electrolytes may be useful for certain types of high-voltage cathode materials. In some cases, the electrolytes may include ion dissociation compounds that can dissociate tight ion pairs. Non-limiting examples of ion dissociation compounds include trialkyl phosphates, sulfones, or the like. Other aspects of the invention are generally directed to devices including such electrolytes, methods of making or using such electrolytes, kits including such electrolytes, or the like.

FIELD

The present invention generally relates to electrolytes for use invarious electrochemical devices.

BACKGROUND

Accompanying the rise of energy densities of lithium-ion batteries(LIBs) and the expansions of scale, high-voltage cathode materials havebeen extensively developed, but are limited by the lack of appropriateelectrolytes having suitable electrochemical stabilities at highoxidation potential. In addition, safety issues in lithium batteries mayarise, for example, from the use of mixed flammable solvents such ascarbonate/ether as solvent systems, which, when overcharged,short-circuited, over-heated, etc., can lead to serious accidents bycatching on fire, burning, or even exploding, etc. Thus, appropriateelectrolytes which are safe, and which have electrochemical stability athigh oxidation potentials, e.g., suitable for high-voltage lithiumbatteries and other applications, are still needed.

SUMMARY

The present invention generally relates to electrolytes for use invarious electrochemical devices. Examples of suitable electrochemicaldevices such as batteries, capacitors, sensors, condensers,electrochromic elements, photoelectric conversion elements, etc. In somecases, the electrolytes are relatively safe to use; for example, theelectrolytes may be resistant to overheating, catching on fire, burning,exploding, etc. In some embodiments, such electrolytes may be useful forcertain types of high-voltage cathode materials. Non-limiting examplesof such high-voltage cathode materials include LiNi_(0.5)Mn_(1.5)O₄(LNMO), LiCoPO₄ (LCP), layered Li—Ni—Co—Mn oxides, (NCM), layeredLi—Ni—Co—Al oxides (NCA), etc. The subject matter of the presentinvention involves, in some cases, interrelated products, alternativesolutions to a particular problem, and/or a plurality of different usesof one or more systems and/or articles.

In one aspect, the present disclosure generally relates to variouselectrolytes based on ion dissociation compounds. As discussed herein,an ion dissociation compound can include any organic compound which candissociate tight ion pairs. In some embodiments, the ion dissociationcompound may also be able to chemically complex to an ion dissociatedfrom the tight ion pair. In some embodiments, the ion dissociationcompounds can be flame retardant. Non-limiting examples of iondissociation compounds include trialkyl phosphates, sulfones, analogs ofsulfone, or the like. Additional examples are also discussed below. Inone embodiment, the present invention is generally directed to anelectrolyte. In one set of embodiments, the electrolyte comprises alithium salt, an ion dissociation compound, and a polymer. In somecases, the polymer comprises a product of a crosslinking reactionincluding a polymer selected from the group consisting of:

where R₁ comprises a structure selected from the group consisting of:

where n is an integer between 1 and 10,000, inclusive; where m is aninteger between 1 and 5,000, inclusive; where R₂, R₃, R₄, R₅, and R₆ areeach independently selected from the group consisting of:

and where * indicates a point of attachment.

In another aspect, the present invention is generally directed to amethod of making a device. In one set of embodiments, the methodcomprises mixing a liquid electrolyte and a polymer precursor into acell, the liquid electrolyte comprising a lithium salt and an iondissociation compound, and solidifying the liquid electrolyte within thecell to form a solid electrolyte. In some cases, the polymer precursorcomprises a structure selected from the group consisting of:

wherein R₁ comprises a structure selected from the group consisting of:

wherein n is an integer between 1 and 10,000, inclusive; wherein m is aninteger between 1 and 5,000, inclusive; wherein R₂, R₃, R₄, R₅, and R₆are each independently selected from the group consisting of:

and wherein * indicates a point of attachment.

Some embodiments are generally directed to various high oxidationpotential electrolytes comprising a polymer comprising a product of acrosslinking reaction including a polymer selected from the groupconsisting of:

where R₁ comprises a structure selected from the group consisting of:

where n is an integer between 1 and 10,000, inclusive; where m is aninteger between 1 and 5,000, inclusive; where R₂, R₃, R₄, R₅, and R₆ areeach independently selected from the group consisting of:

and where * indicates a point of attachment.

In one aspect, the present disclosure encompasses methods of making oneor more of the embodiments described herein, for example, electrolytesbased on ion dissociation compounds. In another aspect, the presentdisclosure encompasses methods of making a solid electrochemical device.

In some cases, the electrolyte may be a high oxidation potentialelectrolyte. For example, in one set of embodiments, the method includesmixing a polymer with a solvent to form a slurry, removing the solvent,and curing the slurry to form a solid electrolyte.

In yet another aspect, the present invention encompasses methods ofmaking one or more of the embodiments described herein, for example,electrolytes for use in various electrochemical devices. In stillanother aspect, the present invention encompasses methods of using oneor more of the embodiments described herein, for example, electrolytesfor use in various electrochemical devices, for example, based on iondissociation compounds.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1 illustrates safety performance curves of an electrolyte inaccordance with certain embodiments of the disclosure;

FIG. 2 illustrates cycling performance curves of an electrolyteaccording to some embodiments of the disclosure;

FIG. 3 illustrates electrochemical stability curves of an electrolyte inaccordance with certain embodiments of the disclosure; and

FIG. 4 illustrates cycling performance curves of an electrolyte inaccordance with other embodiments of the disclosure.

DETAILED DESCRIPTION

The present invention generally relates to electrolytes for use invarious electrochemical devices. In some cases, the electrolytes arerelatively safe to use; for example, the electrolytes may be resistantto overheating, catching on fire, burning, exploding, etc. In someembodiments, such electrolytes may be useful for certain types ofhigh-voltage cathode materials. In some cases, the electrolytes mayinclude ion dissociation compounds that can dissociate tight ion pairs.Non-limiting examples of ion dissociation compounds include trialkylphosphates, sulfones, or the like. Other aspects of the invention aregenerally directed to devices including such electrolytes, methods ofmaking or using such electrolytes, kits including such electrolytes, orthe like.

In one aspect, the present invention is generally directed toelectrolyte materials comprising electrolyte salts such as lithium orsodium salts, ion dissociation compounds, and polymers. In someembodiments, these are generally related to various high oxidationpotential electrolytes suitable for various electrochemical devices. Insome cases, such electrolytes may exhibit better ionic conductivities.For example, ions such as lithium ions may be conducted faster and/ormore efficiently within the electrolyte. This may be useful, forexample, for faster charging/discharging of the electrochemical device.

Certain embodiments include an ion dissociation compound. The iondissociation compound can be an organic compound. In some embodiments,the ion dissociation compound can dissociate ion pairs present insolution (such as lithium ions from a lithium NMC compound), and in somecases, form a chemical complex with an ion from the ion pair (e.g., suchas with a lithium ion). Without wishing to be bound by any theory, it isbelieved that the complex forms due to coordinate chemistry; forexample, the P═O and S═O groups in trialkyl phosphates or sulfones,respectively, can coordinate to the Li cation to form a chemicalcomplex. Non-limiting examples of ion dissociation compounds includeflame retardants, phosphates including organophosphates, sulfones, polaraprotic solvents, or the like. These ion dissociation compounds, andtheir reactions, are discussed in more detail below.

In some embodiments, the polymer may be formed from polymerizationreactions comprising one or more of the following monomers:

where R₁ can be one of the following groups:

where n is an integer between 1 and 10000, m is a integer between 1 and5000, and R₂ to R₆ can each independently be one of the followingstructures:

Other monomers may also be polymerized into the polymer in some cases,e.g., in addition to these. In addition, in some cases, theincorporation of urea or carbamate functional groups with UVcrosslinking can be used to improve mechanical properties and/orelectrochemical performance. Additional examples of polymers include,but are not limited to, those described in U.S. patent application Ser.No. 16/240,502, filed Jan. 4, 2019, entitled “Polymer SolidElectrolytes,” incorporated herein by reference in its entirety.

In certain embodiments, an electrode material may surround byelectrolyte, e.g., filling in porous spaces within the electrode. Forexample, one aspect is generally directed to an electrochemical devicecomprising an electrode comprising particles. Some or all of theparticles may be surrounded by an electrolyte, such as a solidelectrolyte. In some cases, at least some of the pores or intersticesbetween the particles may be filled by an electrolyte. Since theparticles can be surrounded by electrolyte such that at least some ofthe pores or interstices are filled by electrolyte, contact between theparticles and the electrolyte may be very close. This may allow theinternal resistance of the electrochemical device to be lower, which mayallow the electrochemical device to exhibit higher capacities. Examplesof such electrodes may be found, e.g., in a US patent application filedon even date herewith, entitled “Electrodes for Lithium-Ion Batteriesand Other Applications,” incorporated herein by reference in itsentirety.

In some cases, such electrolyte materials may be used in electrochemicaldevices such as batteries, capacitors, sensors, condensers,electrochromic elements, photoelectric conversion elements, etc. Forexample, in certain embodiments, electrolyte materials such as thosedescribed herein may be used to create safer, longer-life lithiumbatteries.

It should be understood that other embodiments are also possible inaddition to the above discussion. For instance, more generally, variousaspects of the invention are directed to electrolytes for use in variouselectrochemical devices, including electrolytes containing iondissociation compounds.

As mentioned, in certain embodiments, an ion dissociation compound ispresent in an electrolyte within an electrochemical device. Withoutwishing to be bound by any theory, it is believed that the iondissociation compound is one that can dissolve Li salts and/or helprelease ions, such as those bound to ion pairs (for example, lithiumions from a lithium NMC compound), and allow the ions to enter solution.Thus, an ion dissociation compound is one that can increase thesolubility limits of Li in a solution, relative to the absence of theion dissociation compound in the solution. This may, for example, allowmore ions to participate in charging/discharging of the electrochemicaldevice, which can lead to improvements such as electrolytes withimproved oxidation potentials, increased ionic conductivities, higherflash points, or higher working temperatures, etc., as discussed below.A variety of compounds may be used as the ion dissociation compound. Insome case, the ion dissociation compound is an organic compound.Non-limiting examples of ion dissociation compounds include flameretardants, phosphates including organophosphates, sulfones, polaraprotic solvents, or the like.

For example, according to one set of embodiments, the ion dissociationcompound comprises a sulfone. The sulfone may have a structureR²—SO₂—R¹, where the R's may be the same or different. Each R may be,for example, a hydrocarbon chain, such as an alkyl (substituted orunsubstituted), an alkenyl (substituted or unsubstituted), an alkynyl(substituted or unsubstituted), or the like. Specific non-limitingexamples of sulfones include divinyl sulfone, allyl methyl sulfone,butadiene sulfone, or ethyl vinyl sulfone. In some cases, sulfones suchas these can also be used as crosslinking agents, e.g., since theycontain double bonds, e.g., for radical polymerizations. Additionalexamples of sulfones include, but are not limited to, dimethyl sulfone,diphenyl sulfone, methyl phenyl sulfone, isopropyl sulfone, trimethylenesulfone, tetramethylene sulfone, diethyl sulfone, ethyl methyl sulfone,or the like. In one set of embodiments, the sulfone may be present at nomore than 0.3 wt %, no more than 0.2 wt %, no more than 0.1 wt %, etc.

In some cases, the ion dissociation compound may comprise a polarsolvent, such as a polar aprotic solvent. The polar aprotic solvent may,in some cases, have high thermal and/or voltage stability, e.g., whenused as electrolyte solvent. The aprotic solvent may in some cases lackO—H and N—H bonds. Non-limiting examples of polar aprotic solventsinclude ethylene carbonate, or sulfones such as those discussed herein.The polarity of the solvent may be one with a relatively dipole momentof between 1 and 5.5, e.g., of at least 1.5 at least 1.75, at least 2,at least 3, at least 4, at least 5, and/or no more than 5.5, no morethan 4.5, no more than 3.5, no more than 2.5, or no more than 1.5. Thepolar aprotic solvent may be able to solvate ions via their large dipolemoments.

In another set of embodiments, the ion dissociation compound comprises aflame retardant. A variety of flame retardants are commerciallyavailable. Non-limiting examples of suitable flame retardants includenitrogen-containing flame retardants, silicon-containing flameretardants, fluorine-containing flame retardants (e.g., methyldifluoroacetate, and difluoroethyl acetate), composite flame-retardantadditives, organophosphorus flame retardants (for example, trialkylphosphate, for example, triethyl phosphate or trimethyl phosphate), orthe like. In one set of embodiments, the flame retardant may be presentat no more than 0.3 wt %, no more than 0.2 wt %, no more than 0.1 wt %,etc. Those of ordinary skill in the art will be able to identifysuitable flame retardants, for example, as is discussed in Beard andAngeler, “Flame Retardants: Chemistry, Applications, and EnvironmentalImpacts,” in Handbook of Combustion, 2010 or Hyung, et al.,“Flame-retardant additives for lithium-ion batteries,” J. Power Sources,119-121:383-387, 2003.

In some cases, a flame retardant can be used to improve safety. Forexample, a flame retardant can be chosen that has a high boiling point(e.g., between 100 and 300° C.), a high flash point (e.g., between 50°C. and 250° C.), a low melting point (e.g., between −50° C. and 70° C.),a high dielectric constant (e.g., between 1 and 80 at 25° C.), goodstability, and/or low cost, etc. A flame retardant can also be used insome cases to prevent or inhibit fire and/or explosion, e.g., caused bythe excessive rise of temperature in the battery.

In one set of embodiments, an ion dissociation compound, such as asulfone, may be used in combination with various lithium salts or ions,or other salts or ions, e.g., as is discussed herein. Examples of suchlithium salts include, but are not limited to, lithiumhexafluorophosphate (LiPF₆), lithium bis(fluorosulfonyl)imide (LiFSI)and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), a highlyconductive lithium salt with an anion that has strong tendency to donatefluorine. In some cases, the combination of a lithium salt and the iondissociation compound may exhibit synergistic interphase formationmechanisms, such as CEI or SEI. Together, these interphase formationsmay allow stable coupling of the electrodes. For example, a stableconfiguration of a graphitic anode and a high-voltage cathode over anextended temperature range may be achieved in accordance with certainembodiments.

In addition, the improved oxidation potential of an electrolyte, e.g.,in association with an ion dissociation compound such as is discussedherein, may provide enhanced stability in certain embodiments in liquidand/or solid electrolytes. The ion dissociation compound may includesulfone or other compounds such as is described herein. Suchelectrolytes may be used, for example, for safe, longer-life and/orhigher voltage lithium batteries.

In some embodiments, an electrolyte salt may be present. These mayinclude alkali metal salts, such as lithium, sodium, or magnesium salts.Specific non-limiting examples of lithium salts include LiTFSI, LiFSI,LiBOB, LiPF₆, LiBF₄, LiClO₄, LiAsF₆, LiN(CF₃SO₂)₂, LiC(CF₃SO₂)₃, LiDFOB,LiF, LiCl, LiBr, LiI, Li₂SO₄, LiNO₃, Li₃PO₄, Li₂CO₃, LiOH, lithiumacetate, lithium trifluoromethyl acetate, lithium oxalate, etc. Otherexamples include, but are not limited to, quaternary ammonium salts,quaternary phosphonium salt, transition metal salts, or salts ofprotonic acids. Non-limiting examples of protonic acids includedimethyldioctadecylammonium chloride, tetraphenylphosphonium chloride,cobalt sulfate, lithium sulfate, etc.

In some cases, the electrolyte salt such as those described herein canbe present at a concentration of at least 1 M, at least 2 M, at least 3M, at least 4 M, at least 5 M, at least 6 M, at least 7 M, at least 8 M,at least 9 M, at least 10 M, and/or no more than 10 M, no more than 9 M,no more than 8 M, no more than 7 M, no more than 6 M, no more than 5 M,no more than 4 M, no more than 3 M, no more than 2 M, no more than 1 M,etc. Combinations of any of these are also possible in some embodiments,e.g., the electrolyte salt may be present at between 1 M and 3 M.

In one set of embodiments, the electrolyte salt may be present at a molefraction of at least 0.01, at least 0.03, at least 0.05, at least 0.1,at least 0.13, at least 0.15, at least 0.2, at least 0.23, at least0.25, at least 0.3, at least 0.33, at least 0.35, at least 0.4, at least0.43, at least 0.45, at least 0.5, at least 0.53, at least 0.55, atleast 0.6, at least 0.63, at least 0.65, at least 0.7, and/or no morethan 0.7, no more than 0.65, no more than 0.63, no more than 0.617, nomore than 0.6, no more than 0.55, no more than 0.53, no more than 0.5,no more than 0.45, no more than 0.43, no more than 0.4, no more than0.35, no more than 0.33, no more than 0.3, no more than 0.25, no morethan 0.23, no more than 0.2, no more than 0.15, no more than 0.13, nomore than 0.1, etc.

Controlling the electrolyte salt concentration may be an effectivestrategy to obtain certain functionalities of liquid electrolytes,including wide electrochemical stability windows. For example,electrolytes based on concentrated LiTFSI in organic phosphates mayexhibit unusual capabilities in enabling reversible cycling of Li⁺ ionsin carbonaceous electrodes. For example, the enhanced solvation inhigh-concentration electrolytes (HCEs) (e.g., greater than 0.5 M,greater than 1.2 M, or greater than 3 M in some cases) can effectivelystabilize the ion dissociation compound molecules and facilitate theformation of a salt-derived SEI that may mitigate anode and electrolytedegradation during extended cycling. Without wishing to be bound by anytheory, it is believed that high-concentration electrolytes may indicatemore ion dissociation compound molecules coordinated with Li ions; sincethe ion dissociation compound molecules can be reduced at a Li metalsurface, the reduction of those free molecules may be beneficial forstabilizing the Li metal surface.

In addition, in some cases, a polymer may also be present. In somecases, a polymer such as those described herein can be present at aconcentration of at least 1 wt %, at least 2 wt %, at least 3 wt %, atleast 4 wt %, at least 5 wt %, at least 6 wt %, at least 7 wt %, atleast 8 wt % at least 9 wt %, at least 10 wt %, at least 11 wt %, atleast 12 wt %, at least 13 wt %, at least 14 wt %, at least 15 wt %, atleast 16 wt %, at least 17 wt % at least 18 wt % at least 19 wt % atleast 20 wt %, 21 wt %, at least 22 wt %, at least 23 wt %, at least 24wt %, at least 25 wt %, at least 26 wt %, at least 27 wt %, at least 28wt % at least 29 wt %, at least 30 wt %, at least 31 wt %, at least 32wt %, at least 33 wt %, at least 34 wt %, at least 35 wt %, at least 36wt %, at least 37 wt % at least 38 wt % at least 39 wt % at least 40 wt%, and/or no more than 40 wt %, no more than 39 wt %, no more than 38 wt%, no more than 37 wt %, no more than 36 wt %, no more than 35 wt %, nomore than 34 wt %, no more than 33 wt %, no more than 32 wt %, no morethan 31 wt %, no more than 30 wt %, no more than 29 wt %, no more than28 wt %, no more than 27 wt %, no more than 26 wt %, no more than 25 wt%, no more than 24 wt %, no more than 23 wt %, no more than 22 wt %, nomore than 21 wt %, no more than 20 wt %, no more than 19 wt %, no morethan 18 wt %, no more than 17 wt %, no more than 16 wt %, no more than15 wt %, no more than 14 wt %, no more than 13 wt %, no more than 12 wt%, no more than 11 wt %, no more than 10 wt %, no more than 9 wt %, nomore than 8 wt %, no more than 7 wt %, no more than 6 wt %, no more than5 wt %, no more than 4 wt %, no more than 3 wt %, no more than 2 wt %,no more than 1 wt %, etc.

Various polymers can be used. The polymer may include one or moreco-polymers. It may be desirable that the polymer be conducting,although some polymers may be non-conducting. More than one polymer maybe present in some cases.

The molecular weight of the polymer is not particularly limited, and maybe any of a broad range of molecular weights. For example, the molecularweight may be at least 100, at least 200, at least 300, at least 500, atleast 1,000, at least 3,000, at least 10,000, at least 30,000, at least100,000, at least 300,000, at least 1,000,000, etc. In some cases, themolecular weight may be no more than 10,000,000, no more than 3,000,000,no more than 1,000,000, no more than 300,000, no more than 100,000, nomore than 30,000, no more than 10,000, no more than 3,000, no more than1,000, no more than 500, no more than 300, etc. Combinations of any ofthese are also possible e.g., the molecular weight may be between 200and 1,000. The molecular weight may be determined as a number averagemolecular weight.

Non-limiting examples of polymers include poly(ethylene) (PE),poly(ethylene oxide) (PEO), poly(propylene) (PP), poly(propylene oxide),polymethyl methacrylate (PMMA), polyacrylonitrile (PAN),poly(bis(methoxy ethoxyethoxide)-phosphazene), poly(dimethylsiloxane)(PDMS), cellulose, cellulose acetate, cellulose acetate butylate,cellulose acetate propionate, polyvinylidene difluoride (PVdF),polyvinylpyrrolidone (PVP), polystyrene, sulfonate (PSS),poly(vinylidene chloride), polypropylene oxide, polyvinylacetate,polytetrafluoroethylene (e.g., Teflon), poly(ethyleneterephthalate)(PET), polyimide, polyhydroxyalkanoate (PHA), PEO containing co-polymers(e.g., polystyrene (PS)-PEO copolymers and poly(methyl methacrylate)(PMMA)-PEO copolymers), poly(acrylonitrile-co-methylacrylate), PVdFcontaining co-polymers (e.g.,polyvinylidenefluoride-co-hexafluoropropylene(PVdF-co-HFP), PMMAco-polymers (e.g. poly(methylmethacrylate-co-ethylacylate)), or thelike. Derivatives of any of these may also be included. In variousexamples, the polymeric material is a combination of two or more ofthese polymers.

The polymer can have various structures (e.g., secondary structures). Invarious examples, the polymer may be amorphous, crystalline, or acombination thereof. It may be desirable in some embodiments that thepolymer(s) and/or copolymers have low crystallinity. For example, thecrystallinity may be less than 70%, less than 60%, less than 50%, lessthan 40%, or less than 30%. The crystallinity can be measured, forexample, using DSC by comparing the exothermic energy of thecrystallization process for a semicrystaline polymer with the energy ofprefect crystal which is calculated based on the crystallization.

In some cases, a polymer may exhibit improved properties due to theaddition of functional groups such as urea and/or carbamate moietieswithin the polymer, e.g., within the backbone structure of the polymer.In some cases, the urea and/or carbamate moieties may be crosslinkedtogether, and/or to other polymers, e.g., as described herein. Withoutwishing to be bound by any theory, it is believed that groups such asurea, urethane, or carbamate contain both hydrogen bond donors andacceptors, which may lead to improvements in properties such asmechanical and/or electrochemical properties, e.g., as discussed herein.For instance, urea linkers with rigid bonding may help to improvemechanical strength. In addition, the hydrogen bonds may help todissociate lithium salts, which may lead to improved ionic conductivity.

In some embodiments, groups such as urea, urethane, or carbamate may bepresent in the backbone of the polymer, for example, as a linker betweena middle polymeric fragment and two acrylic ends. The urea and/orcarbamate may be provided within the polymer using differentcombinations of functional groups, such as amine and carbamate, oralcohol and isocyanate, during formation of the polymer. Such groups maybe present next to each other, and/or some of the groups may beseparated by spacer groups, e.g., between the urea and/or carbamate, andan acrylate.

Non-limiting examples of polymers include those created by polymerizingone or more of the following polymer precursors, and/or otherprecursors:

In these structures, Ri may be selected to allow complexation with saltsor ions, e.g., to produce a polymer/salt complex that can act as anelectrolyte. For example, Ri may include charged moieties, and/ormoieties that are uncharged but are readily ionizable to produce acharge, e.g., at acidic or alkaline pH's (for instance, at pH's of lessthan 5, less than 4, less than 3, or less than 2, or greater than 9,greater than 10, greater than 11, or greater than 12). Specific examplesof R₁ include, but are not limited to, the following (where * indicatesa point of attachment):

In addition, in some cases, 2, 3, 4, or more of the following may bepresent simultaneously within the Ri structure, e.g., as copolymers. Forexample, they may be present in alternating, block, random or othercopolymer structures to define the Ri moiety. In some cases, 2, 3, 4, ormore polymers may be present, and in some cases may be crosslinkedtogether, e.g., as discussed herein.

In these structures n and/or m (as applicable) may each be an integer.In some cases, n and/or m may each be less than 100,000, less than50,000, less than 30,000, less than 10,000, less than 5,000, less than3,000, less than 1,000, less than 500, etc. In certain cases, n and/or mmay be at least 1, at least 3, at least 5, at least 10, at least 30, atleast 50, at least 100, at least 300, at least 500, at least 1,000, atleast 3,000, at least 5,000, at least 10,000, at least 30,000, at least50,000 etc. Combinations of any of these ranges are possible; asnon-limiting examples, n may be an integer between 1 and 10000, m may bean integer between 1 and 5000, n may be an integer between 1000 and5000, m may be an integer between 500 and 1000, etc.

In these structures R₂, R₃, R₄, R₅, and R₆ may each be independentlychosen (as applicable) to make the polymers symmetric or non-symmetric.Examples of R₂, R₃, R₄, R₅, and R₆ include, but are not limited to, oneof the following structures:

Other examples of R₂, R₃, R₄, R₅, and R₆ include, but are not limitedto, an acrylate, an ethylene oxide, an epoxy ethyl group, anisocyanates, a cyclic carbonate, a lactone, a lactams, a vinyl group(CH₂═CH—), or a vinyl derivative (i.e., where 1, 2, or 3 of the H's inthe CH₂═CH— structure have been replaced by an F or a Cl). Non-limitingexamples of cyclic carbonates include ethylene carbonate, propylenecarbonate, fluoroethylene carbonate, etc. In addition, it should beunderstood that these endgroups are provided by way of example only. Ingeneral, the endgroups are not critical, as they typically would notaffect performance in a significant way.

In addition, in one set of embodiments, functional groups such as ureaand/or carbamate may be crosslinked together, e.g., as described herein.For example, such functional groups may be crosslinked together using UVlight, thermoforming or exposure to elevated temperatures (e.g., betweentemperatures of 20° C. and 100° C.), or other methods including thosedescribed herein. In some cases, the incorporation of urea or carbamatefunctional groups can improve mechanical properties, electrochemicalperformances, or the like, such as relatively high ionic conductivities,ion transference numbers, decomposition voltages, tensile strength, orthe like.

In one set of embodiments, the polymer may be present at a mole fractionof at least 0.01, at least 0.02, at least 0.027, at least 0.03, at least0.05, at least 0.1, at least 0.11, at least 0.12, at least 0.13, atleast 0.15, at least 0.2, at least 0.21, at least 0.22, at least 0.23,at least 0.25, at least 0.3, and/or no more than 0.3, no more than 0.25,no more than 0.32, no more than 0.22, no more than 0.21, no more than0.2, no more than 0.15, no more than 0.13, no more than 0.12, no morethan 0.11, no more than 0.1, no more than 0.05, no more than 0.03, nomore than 0.02, no more than 0.01, etc.

In addition, as discussed, more than one polymer may be present, e.g.,as a physical blend and/or as a copolymer, etc., including anycombination of these polymers, and/or other polymers. Still otherexamples of polymers include, those described in U.S. patent applicationSer. No. 16/240,502, filed Jan. 4, 2019, entitled “Polymer SolidElectrolytes,” incorporated herein by reference in its entirety.

In one set of embodiments, the polymer includes a plasticizer, which maybe useful for improve processability of the polymer, and/or controllingthe ionic conductivity and mechanical strength. For example theplasticizer may be a polymer, a small molecule (i.e., having a molecularweight of less than 1 kDa), a nitrile, an oligoether (e.g., triglyme),cyclic carbonate, ionic liquids, or the like. Non-limiting examples ofpotentially suitable plasticizers include ethylene carbonate,succinonitrile, sulfolane, phosphate, or the like. Non-limiting examplesof nitriles include succinonitrile, glutaronitrile, hexonitrile, and/ormalononitrile. Non-limiting examples of cyclic carbonate includeethylene carbonate, propylene carbonate, fluoroethylene carbonate, etc.Non-limiting examples of ionic liquids includeN-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide or1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide. Other non-limitingexamples of plasticizers include polymers such as polyethylene oxide, apolycarbonate, a polyacrylonitrile, a polylactic acid, or the like. Insome cases, the plasticizer may be a polymer that is relativelyhydrophilic, e.g., having a water contact angle of less than 90°. Inaddition, the polymer may be free of sulfur. Other examples ofplasticizers include those described in U.S. patent application Ser. No.16/240,502, filed Jan. 4, 2019, entitled “Polymer Solid Electrolytes,”incorporated herein by reference in its entirety.

In some embodiments, the plasticizer can be present at a mole fractionof at least 0.1, at least 0.11, at least 0.12, at least 0.13, at least0.15, at least 0.2, at least 0.22, at least 0.23, at least 0.25, atleast 0.287, at least 0.3, at least 0.31, at least 0.32, at least 0.33,at least 0.35, at least 0.4, at least 0.5, at least 0.6, at least 0.7,at least 0.8, at least 0.9, at least 0.93, at least 0.95, and/or no morethan 0.95, no more than, no more than 0.93, no more than 0.916, no morethan 0.9, no more than 0.8, no more than 0.7, no more than 0.6, no morethan 0.5, no more than 0.4, no more than 0.35, no more than 0.33, nomore than 0.32, no more than 0.31, no more than 0.3, no more than 0.25,no more than 0.32, no more than 0.22, no more than 0.21, no more than0.2, no more than 0.15, no more than 0.13, no more than 0.12, no morethan 0.11, no more than 0.1, etc.

In one set of embodiments, the solid electrolyte may have a molar ratioof (polymer+crosslinkable oligomer) to plasticizer that is at least1:0.2, at least 1:0.5, at least 1:1, at least 1:1.5, at least 1:2, atleast 1:3, at least 1:5, and/or a ratio that is no more than 1:5, nomore than 1:3, no more than 1:2, no more than 1:1.5, no more than 1:1,no more than 1:0.5, or no more than 1:0.2, Combinations of any of theseare also possible, e.g., the ratio of (polymer+crosslinkable oligomer)to plasticizer may be between 2:1 and 1:2.

In addition, additives or other compounds may also be present, such ascathode protective agents, anode protective agents, anti-oxidativeagents, inorganic additives, etc., in certain embodiments. Non-limitingexamples of inorganic additives include Al₂O₃, SiO₂, SiO_(x), TiO₂,Li₃PS₄, Li₁₀GeP₂S₁₂, Li₇La₃Zr₂O₁₂, Li_(6.4)La₃Zr_(1.4)Ta_(0.6)O₁₂,LiLaTiO₃, Li_(1.3)Al_(0.3)Ti_(1.7)(PO₄)₃,Li_(1.3)Al_(0.3)Ge_(1.7)(PO₄)₃, etc. An example of a cathode protectiveagent is LiDFOB (lithium difluoro(oxalato)borate). An example of ananode protective agent is fluoroethylene carbonate. An example of ananti-oxidative agent is LiBOB (lithium bis(oxalate)borate). Othersimilar compounds will be known by those of ordinary skill in the art.These may be added for a variety of reasons, e.g., to improve otherperformance metrics, such as cyclability. In some cases, an inorganicadditive may be used that contains generally electronegative atoms suchas oxygen, which may attract cations. Thus, for example, ions such asLi⁺ can be relocated relatively more easily than the anions.

In another set of embodiments, the solid electrolyte may contain anorganic carbonate additive. Without wishing to be bound by any theory,in addition to a less-resistive solid electrolyte interphase (SEI), anorganic carbonate can significantly enhance the wettability ofelectrodes in the corresponding electrolytes, which may improve batteryperformance to achieve higher capacities, in comparison withelectrolytes without any organic carbonates additives. For example,organic carbonates may exhibit stability at negative potentials. In somecases, organic carbonates can extend the electrochemical stability ofthe electrolyte towards negative potentials. A small amount of organiccarbonate can significantly improve the battery performance of thepolymer solid electrolyte, e.g., because the presence of organicadditives may increase ionic mobility by lowering lithium coordination,while the electrolyte is still non-flammable.

Non-limiting examples of organic carbonates additives include ethylenecarbonate (EC), vinylene carbonate (VC), fluoroethylene carbonate (FEC),methylene-ethylene carbonate (MEC), 1,2-dimethoxyethane carbonates(DME), diethylene carbonate (DEC),(4R,5S)-4,5-difluoro-1,3-dixolan-2-one (DiFEC). More than one organiccarbonate additive, including these and/or other additives, are alsopossible. The organic carbonate may be present at no more than 15 wt %,no more than 10 wt %, no more than 5 wt %, etc. of the solidelectrolyte.

In one set of embodiments, the electrolyte further comprises astabilization additive. Non-limiting examples of stabilization additivesinclude lithium bis(oxalato)borate (LiBoB) or LiBF₄, etc. In one set ofembodiments, the stabilization additive may be present at no more than0.3 wt %, no more than 0.2 wt %, no more than 0.1 wt %, etc. Withoutwishing to be bound by any theory, stabilization additives may be usefulin certain embodiments for sustaining the voltage of the polymerelectrolyte; as a non-limiting example, an electrolyte may not be ableto sustain a voltage above 3.9 V, but could sustain a voltage of atleast 4.4 V with a stabilization additive.

In some embodiments, the electrolyte may further comprise an initiator,such as a stabilization initiator. Non-limiting examples include benzoylperoxide, 2,2′-azobisisobutyronitrile (AIBN), 4,4-azobis (4-cyanovalericacid) (ACVA), potassium persulfate, or the like. Other examples includeIrgacure initiator, 2,2′-azobis(2-methylpropionitrile), ammoniumpersulfate, or other initiators known to those of ordinary skill in theart. In some embodiments, the initiator may be used to initiate thecrosslink reactions within the polymer, or to otherwise facilitatepolymerization. Those of ordinary skill in the art will know of otherinitiators that can be used, in addition and/or in combination withthese. Many initiators are readily obtainable commercially. In one setof embodiments, the initiator may be present at no more than 0.3 wt %,no more than 0.2 wt %, no more than 0.1 wt %, etc. In some cases, theinitiator may be added to have a mole fraction between 0.001 and 0.01,or other suitable mole fractions to facilitate polymerization.

In some embodiments, the electrolyte may further comprise aphosphine-based additive. Non-limiting examples of phosphine-basedadditives include hexafluoroisopropyl triphosphate, triisopropylethylsulfonyl (pentafluorophenyl) phosphine, or the like. In one set ofembodiments, the phosphine-based additive may be present at no more than0.3 wt %, no more than 0.2 wt %, no more than 0.1 wt %, etc.

In some embodiments, the electrolyte may further comprise an etheradditive. An ether additive may be a linear polymer which helps with iontransport in some cases. For example, the ether additive may increasethe conductivity of the solid electrolyte. Non-limiting examples ofether additives include hydrofluoroether,1,1,2,2-tetrafluoroethyl2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, oligoethylene glycol methyl ether, tetraethylene glycol dimethyl ether,bis(2,2,2-trifluoroethyl) ether, oligo ethylene glycol methyl ether,etc. In one set of embodiments, the ether additive may be present at nomore than 0.3 wt %, no more than 0.2 wt %, no more than 0.1 wt %, etc.

Non-limiting examples of other suitable additives include oligoethyleneglycol, carbonates such as 1,2-dimethoxyethane carbonates,fluoroethylene carbonate, vinylene carbonate, etc.,(4R,5S)-4,5-difluoro-1,3-dixolan-2-one, methylene-ethylene carbonate,prop-1-ene-1,3-sultone, succinic anhydride.

Some additives, such as ethylene carbonate (EC), vinylene carbonate (VC), fluoroethylene carbonate(FEC), (4R,5S)-4,5-difluoro-1,3-dixolan-2-one(DiFEC), methylene-ethylene carbonate (MEC), prop-1-ene-1,3-sultone(PES), and/or succinic anhydride (SA), may be able to preferentiallybreak down and undergo polymerization and ion-exchange reactions at theanode/electrolyte interface to produce a solid-electrolyte-interphase(SEI) with desirable chemical composition and physical properties.Without wishing to be bound by any theory, a stable SEI may, in somecases, be able to accommodate cyclic volume changes at the anode duringcharge (addition) and discharge (removal) of metal atoms to theelectrode.

In some cases, additives such as those described herein can be presentat a weight percentage of at least 1 wt %, at least 2 wt %, at least 3wt %, at least 4 wt %, at least 5 wt %, at least 6 wt %, at least 7 wt %, at least 8 wt % at least 9 wt % , at least 10 wt %, at least 11 wt %,at least 12 wt %, at least 13 wt %, at least 14 wt %, at least 15 wt % ,at least 16 wt % , at least 17 wt % at least 18 wt % at least 19 wt % atleast 20 wt % , and/or no more than 20 wt %, no more than 19 wt %, nomore than 18 wt %, no more than 17 wt %, no more than 16 wt %, no morethan 15 wt %, no more than 14 wt %, no more than 13 wt %, no more than12 wt %, no more than 11 wt %, no more than 10 wt %, no more than 9 wt%, no more than 8 wt %, no more than 7 wt %, no more than 6 wt %, nomore than 5 wt %, no more than 4 wt %, no more than 3 wt %, no more than2 wt %, no more than 1 wt %, etc.

In some cases, electrolytes such as those described herein may providecertain beneficial properties, such as surprisingly high ionicconductivities, compared to other solid electrolytes. For example, thepolymer solid electrolyte may exhibit ionic conductivities of at least10⁻⁸ S/cm, at least 2×10⁻⁸ S/cm, at least 3×10⁻⁸ S/cm, at least 5×10⁻⁸S/cm, at least 10⁻⁷ S/cm, at least 2×10⁻⁷ S/cm, at least 3×10⁻⁷ S/cm, atleast 5×10⁻⁷ S/cm, at least 10⁻⁶ S/cm, at least 2×10⁻⁶ S/cm, at least3×10⁻⁶ S/cm, at least 5×10⁻⁶ S/cm, at least 10⁻⁵ S/cm, at least 2×10⁻⁵S/cm, at least 3×10⁻⁵ S/cm, at least 5×10⁻⁵ S/cm, at least 10⁻⁴ S/cm, atleast 0.8×10⁻⁴, at least 1.1×10⁻⁴, at least 1.2×10⁻⁴, at least 1.4×10⁻⁴,at least 1.6×10⁻⁴, at least 2×10⁻⁴ S/cm, at least 3×10⁻⁴ S/cm, at least5×10⁻⁴ S/cm, at least 10⁻³ S/cm, at least 2×10⁻³ S/cm, at least 3×10⁻³S/cm, at least 5×10⁻³ S/cm, etc. In one embodiment, for example, thepolymer solid electrolyte has ionic conductivity in between 2.1×10⁻⁶S/cm and 5.2×10⁻⁶ S/cm. In another embodiment, the ionic conductivitymay be between 10⁻⁸ and 10⁻² S/cm. Without wishing to be bound by anytheory, it is believed that liquid-level ionic conductivity can beachieved if the physical integrity of polymer solid electrolytes wereensured by using a small amount of polymers. Ionic conductivities can bedetermined, for example, with a 2032 coin cell, using stainless steel asworking electrode and Li metal as reference electrode, where the ionicconductivity is calculated from bulk resistance in impedance spectrum ina potentiostatic mode with a scanning frequency is from 1 MHz to 1 Hz.

As another example, the electrode may exhibit a mass loading of at least1 mA h/cm², 1.5 mA h/cm², 2 mA h/cm², 2.5 mA h/cm², 3 mA h/cm², 3.5 mAh/cm², 4 mA h/cm², 4.5 mA h/cm², 5 mA h/cm², 5.5 mA h/cm², 6 mA h/cm²,etc. The mass loading is a measure of the design area capacity of theelectrode. The area is the area of the electrode. This may bedetermined, for example, by weighing the electrode, calculating theactive material content of the electrode (e.g., the number of ions itcan contain), then calculating the design capacity according to theactive material content.

In addition, in some embodiments, the electrolytes such as thosedescribed herein may provide relatively high oxidation potentials.Electrolytes with relatively high oxidation potentials may beparticularly useful, for example, in applications where higher voltagesare required. In certain cases, the oxidation potential of the polymersolid electrolyte may be at least 0.3 V, at least 0.4 V, at least 0.5 V,at least 0.6 V, at least 0.7 V, at least 0.8 V, at least 0.9 V, at least1 V, at least 1.5 V, at least 2 V, at least 2.5 V, at least 3 V, atleast 3.5 V, at least 3.8 V, at least 4 V, at least 4.5 V, at least 5.0V, at least 5.1 V, or at least 5.5 V. Oxidation potentials can be testedusing standard techniques known to those of ordinary skill in the art,such as cyclic voltammetry. Without wishing to be bound by any theory,it is believed that electrolytes with high oxidation potentials may berelatively stable at high voltages.

In addition, in some embodiments, electrolytes such as those describedherein may provide relatively high flash points. The flash point is thetemperature at which a material (e.g., the electrolyte) will ignite ifgiven an ignition source (e.g., a flame or a spark). Electrolytes withrelatively high flash point may be particularly useful, for example, inapplications where higher flash point are required. In certain cases,the flash point of the electrolyte may be at least 85° C., least 90° C.,at least 93.3° C., at least 95° C., at least 100° C., at least 105° C.,at least 110° C., at least 115° C., at least 120° C., at least 125° C.,at least 130° C., at least 135° C., at least 140° C., at least 145° C.,at least 150° C., at least 155° C., at least 160° C., at least 165° C.,at least 170° C., at least 175° C., at least 180° C., at least 185° C.,at least 190° C., at least 195° C., at least 200° C., etc. Flash pointscan be tested using standard techniques known to those of ordinary skillin the art. Without wishing to be bound by any theory, it is believedthat electrolytes with relatively high flash point can be used at hightemperatures, which may help the improve the safety of the electrolytes.

In addition, in some embodiments, electrolytes such as those describedherein may be used or worked at relatively high temperatures, e.g.,working temperatures of at least 85° C., least 90° C., at least 93° C.,at least 95° C., at least 100° C., at least 105° C., at least 110° C. ,at least 115° C., at least 120° C., at least 125° C., at least 130° C.,at least 135° C., at least 140° C., at least 145° C., at least 150° C.,at least 155° C., at least 160° C., at least 165° C., at least 170° C.,at least 175° C., at least 180° C., at least 185° C., at least 190° C.,at least 195° C., at least 200° C., etc. In some cases, the electrolytemay be highly stable at relatively high temperatures. The workingtemperature of the electrolyte may be controlled by other parameters,such as its electrochemical stability at elevated temperature. Theworking temperature may be lower than the flash point.

To determine working temperature, the battery can be tested at roomtemperature (25° C.), where m is the cycle number when the capacity is80% of the capacity after the first cycle. Then the battery can betested at a working temperature T; for example, the battery can betested in an oven with a temperature T, where n is the cycle number whenthe capacity is 80% of the capacity after the first cycle. The workingtemperature is the maximum temperature that still allows the battery tosatisfy the equation 0.3≤n/m≤1. For example, n/m can be 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9, 1, etc.

In some aspects, the present invention is generally directed to anelectrochemical cell, e.g., within an electrochemical device, comprisingan electrolyte material such as those discussed herein. Non-limitingexamples of electrochemical devices include batteries, capacitors,sensors, condensers, electrochromic elements, photoelectric conversionelements, or the like. In one set of embodiments, the electrochemicaldevice is a battery, e.g., an ion-conducting battery. Non-limitingexamples of ion-conducing batteries include lithium-ion conductingbatteries, sodium-ion conducting batteries, magnesium-ion conducingbatteries, and the like. For instance, the lithium-ion battery maycomprise one or more lithium ion electrochemical cells, where some orall of the electrochemical cells has a structure such as is describedherein. In some cases, the battery is a solid-state battery. Theelectrochemical device may also comprise an anode, a cathode, aseparator, etc. Many of these are available commercially. An electrolyteas described herein may be used as the electrolyte of theelectrochemical device, alone and/or in combination with otherelectrolyte materials.

The anode material may be a conducting material. For example, the anodemay comprise a conducting carbon material, such as graphite, hardcarbon, porous hollow carbon spheres and tubes, and the like. Othernon-limiting examples of conducting materials include conducting carbonmaterials, tin and its alloys, tin/carbon, tin/cobalt alloys,silicon/carbon materials, and the like. Non-limiting examples ofconducing carbon materials include graphite, hard carbon porous hollowcarbon spheres and tubes (e.g., carbon nanotubes), and the like. Asother examples, the anode may comprise silicon, tin, carbon,phosphorous, or the like. A wide variety of anodes and anode materialsmay be obtained commercially.

The anode may be a metal in some embodiments. Non-limiting examples ofmetals include lithium metal, sodium metal, magnesium metal, and thelike. Lithium (Li) metal is a promising anode material, e.g., forhigh-energy-density storage systems, because of its high specificcapacity (3860 mA h g⁻¹) and low reduction potential (−3.04 V) versusthe standard hydrogen electrode.

In one embodiment, the anode may comprise a lithium ion-conductingmaterial, such as lithium metal, lithium carbide, Li₆C, a lithiumtitanate (e.g., Li₄Ti₅O₁₂), or the like. In another embodiment, theanode material may comprise a sodium-ion-conducting material, such assodium metal, Na₂C₈H₄O₄, Na_(0.66)Li_(0.22)Ti_(0.78)O₂, or the like. Inyet another embodiment, the anode material may comprise a magnesiumion-conducting material, such as magnesium metal.

A cathode may comprise one or more the electroactive material in certainembodiments. Various electroactive materials can be used, includinglithium ion-conducting material.

In some cases, the cathode may comprise one or more particles. Theparticles may comprise, in certain cases, one or more positiveelectroactive materials. The particles may comprise positive ions suchas lithium, sodium, magnesium, or the like. Examples of particles foruse in cathodes may be seen in a U.S. patent application filed on evendate herewith, entitled “Electrodes for Lithium-Ion Batteries and OtherApplications,” included herein by reference in its entirety.

In one set of embodiments, the cathode may comprise lithium, which maybe present, for instance, as lithium metal and/or lithium salts.Non-limiting examples include lithium cobalt oxide (LCO), lithium nickelmanganese cobalt oxide (NMC) (e.g., LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ orLiNi_(0.5)Co_(0.2)Mn_(0.3)O₂), lithium nickel cobalt manganese aluminumoxide, lithium nickel cobalt aluminum oxide, lithium titanate, metalliclithium, lithium metal oxide, lithium cobalt oxide, lithium manganeseoxides (LMO) (e.g., LiMn₂O₄ and LiNi_(0.5)Mn_(1.5)O₄), lithium ironphosphates (LFP) (e.g., LiFePO₄), LiMnPO₄, LiCoPO₄ (LCP), Li₂MMn₃O₈,wherein M is Fe and/or Co, layered Li—Ni—Co—Mn oxides, (NCM), layeredLi—Ni—Co—Al oxides (NCA), and the like. Combinations of these and/orother compounds are also possible.

As a non-limiting example, the cathode may comprise a positiveelectroactive material that contains various amounts of lithium, nickel,manganese, and cobalt. These may vary independently of each other, e.g.,in the formula Ni_(x)Mn_(y)Co_(z). In some cases, the sum of x, y, and zis 1, i.e., there are no other ions present within the NMC matrixcomposition (other than the alkali metal ions, e.g., lithium) other thanthese three. Thus, z may equal (1−x−y). However, in other cases, the sumof x, y, and z may actually be less than or more than 1, e.g., from 0.8to 1.2, from 0.9 to 1.1, from 0.95 to 1.05, or from 0.98 to 1.02.Additional example values are discussed below. Thus, the material may beoverdoped or underdoped in some cases, and/or contain other ions presentin addition to nickel, manganese, and cobalt.

As an example, the positive electroactive material may have a formula ofLi_(a)(Ni_(x)Mn_(y)Co_(z))O₂. In some cases, a is a numerical value in afirst range between approximately 1.00 and 1.01, x is a numerical valuein a second range between approximately 0.34 and 0.58, y is a numericalvalue in a third range between approximately 0.21 and 0.38, and z is anumerical value in a fourth range between approximately 0.21 and 0.38.Additional example values for each of a, x, y, and z are discussedbelow.

In another set of embodiments, the positive electroactive material cancomprise an electroactive composition that comprises lithium (Li),nickel (Ni), manganese (Mn), and cobalt (Co). The positive electroactivematerial can further include an element M selected from samarium (Sm),lanthanum (La), zinc (Zn) or combinations thereof. In some embodiments,the composition can have a formula ofLi_(a)Mb(Ni_(x)Mn_(y)Co_(z))_(1-b)O₂. In some cases, a may be anumerical value in a first range between approximately 1.00 and 1.01, bis a numerical value in a second range between approximately 0 and 0.08,x is a numerical value in a third range between approximately 0.34 and0.58, y is a numerical value in a fourth range between approximately0.21 and 0.38, and z is a numerical value in a fifth range betweenapproximately 0.21 and 0.38. Additional example values for each of a, b,x, y, and z are discussed below.

In any of the structures described above or herein, in some cases, x(e.g., nickel) may be at least 0.5, at least 0.55, at least 0.6, atleast 0.65, at least 0.7, at least, 0.75, at least 0.8, at least 0.85,at least 0.9, at least 0.95, etc. In some embodiments, x may be no morethan 0.95, no more than 0.9, no more than 0.85, no more than 0.8, nomore than 0.75, no more than 0.7, no more than 0.65, no more than 0.6,no more than 0.55, no more than 0.5, etc. In certain embodiments,combinations of any these are possible. For example, x may be between0.7 and 0.9.

In some cases, y (e.g., manganese) may be at least 0.05, at least 0.1,at least 0.15, at least 0.2, at least 0.25, at least 0.3, at least 0.35,at least 0.4, at least 0.45, at least 0.5, etc. In some embodiments, ymay be no more than 0.5, no more than 0.45, no more than 0.4, no morethan 0.35, no more than 0.3, no more than 0.25, no more than 0.2, nomore than 0.15, no more than 0.1, no more than 0.05, etc. In certainembodiments, combinations of any these are possible. For example, y maybe between 0.05 and 0.15.

In some cases, z (e.g., cobalt) may be at least 0.05, at least 0.1, atleast 0.15, at least 0.2, at least 0.25, at least 0.3, at least 0.35, atleast 0.4, at least 0.45, at least 0.5, etc. In some embodiments, z maybe no more than 0.5, no more than 0.45, no more than 0.4, no more than0.35, no more than 0.3, no more than 0.25, no more than 0.2, no morethan 0.15, no more than 0.1, no more than 0.05, etc. In certainembodiments, combinations of any these are possible. For example, z maybe between 0.05 and 0.15.

In some cases, a (e.g., lithium) may be at least 0.95, at least 0.96, atleast 0.97, at least 0.98, at least 0.99, at least 1.00, at least 1.01,at least 1.02, at least 1.03, at least 1.04, at least 1.05, etc., and/orno more than 1.05, no more than 1.04, no more than 1.03, no more than1.02, no more than 1.01, no more than 1.00, no more than 0.99, no morethan 0.98, no more than 0.97, no more than 0.96, no more than 0.95, etc.Combinations of any of these may also be possible, e.g., a may bebetween 0.99 and 1.03.

In some cases, b may be at least 0.01, at least 0.02, at least 0.03, atleast 0.04, at least 0.05, at least 0.06, at least 0.07, at least 0.08,at least 0.09, at least 0.1, etc. In some embodiments, b may be no morethan 0.1, no more than 0.09, no more than 0.08, no more than 0.07, nomore than 0.06, no more than 0.05, no more than 0.04, no more than 0.03,no more than 0.02, no more than 0.01. b may also be 0 in some cases.Combinations of any of these may also be possible, e.g., a may bebetween 0.07 and 0.09.

Additional examples of positive electroactive materials can be seen inInt. Pat. Apl. Pub. No. WO 2018/112182, entitled “Electroactive Materialfor Lithium-Ion or other Batteries,” or Int. Pat. Apl. Pub. No. WO2017/053275, entitled “Nickel-Based Positive Electroactive Materials,”each of which is incorporated herein by reference in its entirety.

In another aspect, the present disclosure generally relates to methodsof making electrolytes such as those discussed herein. For example, inone set of embodiments, a solid electrolyte may be prepared by mixing aliquid electrolyte and a polymer precursor into a cell, and solidifyingthe liquid electrolyte within the cell to form a solid electrolyte. Theelectrolyte and the polymer precursor may be as discussed herein. Forexample, the electrolyte may comprise a lithium salt and an iondissociation compound. In some cases, a liquid electrolyte and a monomeror polymer may be mixed in a liquid phase, and introduced into apre-assembled cell. Solidification within the cell may occur based onthermal gelation, physical gelation, polymerization, cross-linking, orthe like, e.g., to form a solid electrolyte within the cell.

In some cases, a polymer may be produced by reacting various monomerstogether. Non-limiting examples of monomers include differentcombinations of the structures described herein, for example,methacrylate monomers with different ester groups, such as norbornylmethacrylate. Other examples of esters include, but are not limited to,methyl methacrylate, ethyl methacrylate, butyl methacrylate,2-aminoethyl methacrylate hydrochloride, glycidyl methacrylate,2-(diethylamino)ethyl methacrylate, etc.

In some cases, an initiator may be present, e.g., to facilitatepolymerization. For example, the initiator may include a chemicalinitiator, such as Irgacure initiator,2,2′-azobis(2-methylpropionitrile), ammonium persulfate, or otherinitiators known to those of ordinary skill in the art. In some cases,the initiator may be added to have a mole fraction between 0.001 and0.01, or other suitable mole fractions to facilitate polymerization.

In one set of embodiments, the polymer may be mixed with a solvent toform a slurry, which can be cured to form a solid. In addition, in somecases, more than one polymer may be present in the slurry, e.g., a firstpolymer and a second polymer, which may be added to the slurrysequentially, simultaneously, etc. The polymers may each independentlybe polymers such as those described herein, and/or other suitablepolymers.

Non-limiting examples of suitable solvents include solvents such aswater (e.g., distilled water), methanol, ethanol, or other aqueoussolvents. Other examples of solvents include organic solvents such aspyridine, chloroform, or the like. In some cases, more than one suchsolvent may be present. In addition, after formation of the slurry, thesolvent may be removed, e.g., via techniques such as evaporation.

In addition, in some cases, a plasticizer may be present as well, e.g.,such as succinonitrile, ethylene carbonate, sulfolane, trimethylphosphate, or the like. In addition, in some embodiments, anelectrolytic salt may also be present, for example, an alkali metalsalt, such as lithium or sodium. Specific non-limiting examples oflithium salts include LiTFSI, LiFSI, LiBOB, LiPF₆, LiBF₄, LiClO₄,LiAsF₆, LiN(CF₃SO₂)₂, LiC(CF₃SO₂)₃, LiDFOB, LiF, LiCl, LiBr, LiI,Li₂SO₄, LiNO₃, Li₃PO₄, Li₂CO₃, LiOH, lithium acetate, lithiumtrifluoromethyl acetate, lithium oxalate, etc., or other salts such asthose described herein.

In some embodiments, the slurry may be cured to form a film, such as asolid-state film. For instance, the mixture can be formed into a film bycuring, for example, using UV light, thermoforming, exposure to elevatedtemperatures, or the like. For example, curing may be induced usingexposure to UV light for at least 3 min, at least 5 min, at least 10min, at least 15 min, etc., and/or by exposure to temperatures of atleast 20° C., at least 30° C., at least 40° C., at least 50° C., atleast 60° C., at least 70° C., at least 80° C., at least 90° C., atleast 100° C., etc. As an example, a slurry may be coated or positionedon a surface and/or within a mold, and exposed to UV light to cause thepolymer to cure.

In addition, in some cases, during the curing process, at least some ofthe polymers may also cross-link, e.g., as discussed herein, which insome cases may improve mechanical properties and/or electrochemicalperformance. For example, exposure to UV light may facilitate thecross-linking process. As another example, thermal crosslinking may beused.

Additional discussion of electrolyte fabrication may be seen in Int.Pat. Apl. Pub. No. WO 2018/112182, entitled “Electroactive Material forLithium-Ion or other Batteries,” or Int. Pat. Apl. Pub. No. WO2017/053275, entitled “Nickel-Based Positive Electroactive Materials,”each incorporated herein by reference in its entirety for all purposes.

The following documents are incorporated herein by reference in theirentireties: Int. Pat. Ser. Apl. No. PCT/US16/52627, entitled “HighPerformance Nickel-Based Positive Electroactive Material for aLithium-Ion Battery,” published as Int. Pat. Apl. Pub. No. WO2017/053275; Int. Pat. Apl. Ser. No. PCT/US17/66381, entitled“Electroactive Materials for Lithium-Ion Batteries and OtherApplications,” published as Int. Pat. Apl. Pub. No. WO 2018/112182; Int.Pat. Apl. Ser. No. PCT/US18/18986, entitled “Core-Shell ElectroactiveMaterials,” published as Int. Pat. Apl. Pub. No. WO 2018/156607; U.S.patent application Ser. No. 16/037,041, entitled “Ionomer ElectrodeManufacturing Slurry,” published as U.S. Pat. Apl. Pub. No.2019/0020033; U.S. patent application Ser. No. 16/059,251, entitled“Poly(Lithium Acrylate) and Other Materials for Membranes and OtherApplications,” published as U.S. Pat. Apl. Pub. No. 2019/0051939; U.S.patent application Ser. No. 16/240,502, entitled “Polymer SolidElectrolyte”; and a U.S. patent application filed on even date herewith,entitled “Electrodes for Lithium-Ion Batteries and Other Applications.”

The following examples are intended to illustrate certain embodiments ofthe present invention, but do not exemplify the full scope of theinvention.

EXAMPLE 1

This example provides a description of a safe electrolyte in accordancewith some embodiments of the present disclosure. This example alsoprovides examples of making and charactering such an electrolyte.

The electrolyte was obtained by mixing an ion dissociation compoundtrimethyl phosphate, lithium salts (lithiumbis(trifluoromethanesulfonyl)imide, LiTFSI) and additive in the ratiosdescribed in Table 1 by mechanical stirring at room temperature in theliquid state. Details of the lithium salt and additive are listed inTable 1.

Cycling performance: The electrolyte was assembled in a 2032-coin cellwith lithium foil as the anode, NMC811 as cathode (2 mAh/cm²), acommercial Celgard separator as the separator, with electrolytes basedon carbonate esters for comparison. The cycling test was performed witha Neware cycling tester. The charge/discharge voltage window was from2.8 V to 4.5 V. FIG. 2 illustrates the capacity retention of Example 1-1after 100 cycles at current rate of 0.5 C. The test data is list inTable 1.

Safety: Test Protocol: This test used penetration by a 3 mm stainlesssteel nail with a penetration speed of approximately 80 mm/sec. Thepenetration was perpendicular to the flat face (largest surface areaface) of the cell. The cell was instrumented for voltage and surfacetemperature, both of which were logged at an appropriate interval. FIG.1 illustrates the voltage profile and thermal profile of Example 1-1.

Measurement Equipment & Calibration Data: MY44056108, Datalogger,Agilent 34970A, Last Cal May 18, 2018, Cal Due May 18, 2019.

Pre-Test Information and Data: 1 Ah Pouch Cell was fully charged from2.8 V to 4.5 V, the nail speed (80 mm/sec) was programmed into theactuator.

In-Test Information and Data: ambient temperature: 20.4 ° C., ambienthumidity: 35%.

TABLE 1 Ion Capacity dissociation Additive Li salt Retention Examplecompound (Percentage) Li salt Concentration (100 cycles) Example 1-1Trimethyl 1,2-dimethoxyethane LiTFSI 0.8M 80% phosphate (20%) Example1-2 Trimethyl Tetraethylene glycol LiTFSI 1.0M 75% phosphate dimethylether (10%) Example 1-3 Trimethyl Fluoroethylene LiTFSI 1.2M 83%phosphate carbonate (30%) Comparison EC/DEC N/A LiPF₆   1M 40% Example 1

Comparison Example 1 used a conventional carbonate electrolyte of 1.0 Mlithium hexafluorophosphate (LiPF₆) in a mixture of ethylene carbonate(EC) and diethyl carbonate (DEC) (3:7 by weight). It is highlyflammable.

In Examples 1-1, 1-2, 1-3, the electrolytes used LiTFSI, aflame-retardant trimethyl phosphate. According to FIG. 1 , thetemperature of the sample increased up to 70.6° C. without any fire orexplosion, illustrating that the electrolyte was highly stable with bothLi metal anodes and high-voltage cathodes. Thus, the electrolyte washighly stable and safe, and could be used in systems such ashigh-energy-density Li metal batteries (LMBs). The introduction of theflame retardant trimethyl phosphate could potentially prevent fire andexplosion due to the excessive rise of temperature in the battery,making the electrolyte nonflammable, and thus improving the safety ofthe battery. The low flammable electrolyte could provide enhanced safetyfor lithium metal and lithium ion batteries. The electrolytes could alsobe used in LIBs and other batteries to largely improve their safety andcyclability.

In addition, different additives were used to further improve thecycling performance. For example, in Example 1-1, 20 vol %1,2-dimethoxyethane was introduced; in Example 1-2, 10 vol %tetraethylene glycol dimethyl ether was introduced; and in Example 1-3,30 vol % fluoroethylene carbonate was introduced. Based on the testresults in Table 1 and FIG. 2 , the electrolyte allowed stable cyclingof the Li metal anode (LMA), and greatly enhanced the cyclingperformance of Li/NMC811 batteries (>83% capacity retention after 100cycles at 0.5 C). Without wishing to be bound by any theory, theexcellent electrochemical performance of the electrolyte was believed tobe due to the enhanced stability between the LMA and the well-reservedlocally concentrated Li⁺-FSI⁻-TEP solvation structures, as well as theimproved interfacial reaction kinetics.

Moreover, different Li salts at different concentration in trimethylphosphate can used to prepare such electrolyte. For example, the saltconcentration in the electrolytes can be from 0.5 M to 7 M.

EXAMPLE 2

This example illustrates an electrolyte. The electrolyte was obtained bymixing an ion dissociation compound dimethyl sulfone, additive andlithium salts (lithium bis(trifluoromethanesulfonyl)imide, LiTFSI), inthe ratios described in Table 2 by mechanical stirring at roomtemperature in the liquid state. Electrochemical stabilities and cyclingperformance were determined. The test data is listed in Table 2.

Electrochemical stability (oxidation potential) testing was performedusing cyclic voltammetry measurements with an AC impedance analyzer(Interface 1010E Potentiostate, Gamry). Samples with an area of 1.54 cm²were sealed between stainless-steel plate and lithium foil (referenceelectrode), with commercial electrolytes based on carbonate esters forcomparison. The charge/discharge window range was from 2.8 to 6.0 V witha scan rate of 10 mV/s. The test was conducted at room temperature. FIG.3 illustrates the electrochemical stability curves of the electrolyte ofExample 2-4.

Cycling performance: The measurement methods and conditions were similarto Example 1. Each cell was charged and discharged for 200 cycles.

TABLE 2 Oxidation Ion Additive Potential Capacity dissociation (VolumeLi salt vs. Li/Li+ Retention (%) Example compound Percentage) Li saltConcentration (V) (200 cycle 0.5 C) Example 2-1 Dimethyl None LiTFSI0.8M 5.5 V 60% Example 2-2 Sulfone 1,2- LiTFSI 1.0M 5.0 V 72%dimethoxyethane (5%) Example 2-3 Tetraethylene LiTFSI 1.2M 5.1 V 77%glycol dimethyl ether (15%) Example 2-4 Fluoroethylene LiTFSI 1.8M 5.5 V82% carbonate (5%) Comparison EC/DEC N/A LiPF₆   1M 4.2 V 40% Example 1

Compared with Comparison Example 1, in Example 2, dimethyl sulfone wasintroduced. Dimethyl sulfone is a highly polar aprotic solvent iondissociation compound with high thermal and voltage stability windowswhen used in the electrolyte. According to the test data of theelectrochemical stability in Table 2 and FIG. 3 , the introduction ofthe dimethyl sulfone can improve performance of the electrolyte.

For example, in one aspect, the electrolytes exhibited higher oxidationpotentials (>5.0 V) than the comparison examples, illustrating that theelectrolytes were very stable at high voltages, making them useful forhigh voltage lithium ion cathode materials, such asLiNi_(0.5)Mn_(1.5)O₄.

In another aspect, the electrolytes exhibited a SET (self-extinguishingtime) of <6 s g⁻¹, illustrating that the electrolytes were relativelynon-flammable, and that the safety of the electrolytes was improved.(See below for additional details regarding this test.)

In yet another aspect, the electrolytes exhibited stability towardlithium metal, illustrating that the electrolytes were highly stablewith Li metal anodes, making the electrolyte highly stable and safe foruse in high-energy-density Li metal batteries (LMBs). When dimethylsulfone was used in combination with lithium bis(fluorosulfonyl)imide(LiFSI), a highly conductive lithium salt with an anion that has strongtendency to donate fluorine, the electrolytes exhibited synergisticinterphase formation mechanisms (CEI/SEI). Together, these interphasesallowed stable coupling of a Li metal anode and a high-voltage cathodeover an extended temperature range.

Different additives were also used to further improve cyclingperformance. In Example 2-2, 5 vol % 1,2-dimethoxyethane was introduced;in Example 2-3, 15 vol % tetraethylene glycol dimethyl ether wasintroduced; and in Example 2-4, 15 vol % fluoroethylene carbonate wasintroduced. As shown in Table 2, the additives helped to enhance thecycling performance of Li/NMC811 batteries (>82% capacity retentionafter 200 cycles at 0.5 C). Without wishing to be bound by any theory,the excellent electrochemical performance of the electrolyte wasbelieved to be due to the enhanced stability between the LMA and thewell-reserved locally concentrated Li⁺-FSI⁻-TEP solvation structures, aswell as the improved interfacial reaction kinetics.

Moreover, different Li salts at different concentration in trimethylphosphate can used to prepare such electrolyte. For example, the saltconcentration in the electrolytes can be from 0.5 M to 7 M.

EXAMPLE 3

Example 3-1 to Example 3-4: Examples 3-1 through 3-4 illustrate anelectrolyte. The electrolyte was obtained by mixing a dissociationcompound diethyl sulfone, a certain concentration of lithium salts(lithium bis(trifluoromethanesulfonyl)imide, LiTFSI) (0.5 M in Examples3-1 and 3-3, and 3 M in Example 3-2 and 3-4), 0.5 wt % additive(vinylene carbonate, VC, in Example 3-1 and 3-2, and fluoroethylenecarbonate, FEC, in Example 3-3 and 3-4) by mechanical stirring at roomtemperature in the liquid state.

Example 3-5 to Example 3-12. Examples 3-5 to 3-12 illustrate a polymersolid electrolyte based on sulfur containing ion dissociation compound.The polymer solid electrolyte was obtained by mixing a polymer (10% inExamples 3-5 and 3-6, 20% in Examples 3-7 through 3-12), 1 wt % AIBN asinitiator, a dissociation compound (diethyl sulfone), a certainconcentration of lithium salts (lithiumbis(trifluoromethanesulfonyl)imide, LiTFSI) (0.5 M in Examples 3-5, 3-7,3-9, and 3-11; 3 M in Examples 3-6, 3-8, 3-10, and 3-12), 0.5 wt %additive (vinylene carbonate, VC, in Examples 3-9 and 3-10;fluoroethylene carbonate, FEC, in Examples 3-11 and 3-12; and noadditive in Examples 3-5, 3-6, 3-7, and 3-8) by mechanical stirring atroom temperature in a liquid state. The polymer had the structure shownbelow. Synthesis of the polymer was described in Example 5 of U.S.Provisional Patent Application Ser. No. 62/757,133 (incorporated hereinby reference in its entirety).

Comparison Example 3-1, 3-2, and 3-3. Comparison Example 3-1 used acommercial electrolytes based on carbonate esters, with 1 M lithiumhexafluorophosphate (LiPF₆) in a mixture of ethylene carbonate (EC) anddiethyl carbonate (DEC) (1:1 by weight).

Comparison Examples 3-2 and 3-3 were electrolytes based on conventionalcarbonate. The electrolytes were obtained by mixing the polymer (thesame as the polymer in Examples 3-5 to 3-12), 1% initiatorazobisisobutyronitrile (AIBN), and 1 M lithium hexafluorophosphate(LiPF₆) in a mixture of ethylene carbonate (EC) and diethyl carbonate(DEC) (1:1 by weight). The concentration of the polymer in ComparisonExample 3-2 was 10 wt %, and the concentration of the polymer inComparison Example 3-3 was 20 wt %,

The mixtures in Examples 3-5 to 3-12 and Comparison Examples 3-2 and 3-3were each applied to a PET thin film. In particular, a solid-stateelectrolyte film was obtained by UV-curing for 5 min. Electrochemicalstabilities, electrochemical impedance spectroscopy, cyclingperformance, and safety performance were determined. The test data islisted in Table 3.

Electrochemical stability. The measurement methods and conditions weresimilar to Example 2.

Electrochemical Impedance Spectroscopy. Electrochemical impedancespectroscopy testing was performed by AC impedance analyzer (Interface1010E Potentiostate, Gamry). The samples with an effective area of 1 cm²were placed in 2032 coin-type cells. The ionic conductivity was measuredin the frequency range of 1 MHz to 1 Hz by a bias voltage of 10 mV. Theionic conductivity was calculated with the known thickness and area themembrane.

Cycling performance. The electrolytes were tested in an electrochemicalcell with NCM811 as cathode, and graphite as anode. The measurementmethods and conditions were similar to Example 1.

Self-extinguishing time (SET). A liquid sample is used. The liquidsample can be either immobilized in a porous carrier material or placeddirectly on a dish. The time between the removal of a gas flame andflame self-extinguishment was determined. SET is reported in seconds pergram of sample. The sample can be determined to be “non-flammable” ifthe SET is less than 6 s g⁻¹, “flame-retarded” if the SET is between 6 sg⁻¹ and 20 s g⁻¹, and “flammable” if the SET is greater than 20 s g⁻¹.

TABLE 3 Oxidation Potential Flash Coin Cell 0.5 C Working IonicConductivity vs. Li/Li⁺ Point Capacity Temperature Example (S/cm) (V) (°C.) (mAh/g) Cycling (° C.) Example 3-1 3.2 × 10⁻⁴ >5.0 >170 80 >300 >85Example 3-2 2.8 × 10⁻⁴ 185 Example 3-3 — 112 Example 3-4 2.8 × 10⁻⁴ 175Example 3-5 1.4 × 10⁻⁴ >4.5 — >200 Example 3-6 0.8 × 10⁻⁴ 156 Example3-7 1.2 × 10⁻⁴ — Example 3-8 0.7 × 10⁻⁴ 151 Example 3-9 0.8 × 10⁻⁴ —Example 3-10 0.7 × 10⁻⁴ 162 Example 3-11 0.8 × 10⁻⁴ — Example 3-12 0.7 ×10⁻⁴ 152 Example 3-10 1.1 × 10⁻⁴ >4.5 >170 169 >200 >85 (tested at 85°C.) Comparison Example 1.2 × 10⁻⁴ <4.4 <70 95 poor <40 3-1 ComparisonExample 0.6 × 10⁻⁴ 88 3-2 Comparison Example 0.7 × 10⁻⁴ 72 3-3

Examples 3-1 to 3-12 were tested at room temperature. Example 3-10 wasalso re-tested at 85° C. FIG. 4 illustrates an example comparing theperformance of Example 3-2 and 3-10.

In Examples 3-1 to 3-13, an ion dissociation compound was introduced.The ion dissociation compound was a highly polar aprotic compound, withhigh thermal and voltage stability windows when used in an electrolyte.According to the test data shown in Table 3, the introduction of an iondissociation compound can improve various performances of theelectrolyte.

For example, in one aspect, the electrolytes exhibited higher oxidationpotentials (>5.0 V) than the comparison examples, illustrating that theelectrolytes were very stable at high voltages, making them useful forhigh voltage lithium ion cathode materials, such as LiN₁₀5Mn_(1.5)O₄.

In another aspect, the electrolytes exhibited higher flash points (>170°C.), and SETs (self-extinguishing time) of <6 s g⁻¹, illustrating thatthe electrolyte was relatively non-flammable, and that the safety of theelectrolytes was improved.

In another aspect, the electrolytes exhibited better galvanostaticcycling performance (cycle >300, capacity of 185 mAh/g) in anelectrochemical cell at higher working temperatures (>85° C.) than thecomparison examples. This illustrates that the electrolytes were highlystable at high temperatures, making it a good candidate for hightemperature lithium batteries. The electrolytes also exhibitedacceptable stability toward graphite anode, suggesting that theelectrolytes were highly stable and safe for Li batteries. When the iondissociation compound was used in combination with lithiumbis(trifluoromethanesulfonyl)imide (LiTFSI), a highly conductive lithiumsalt with an anion that had strong tendency to donate fluorine, theelectrolytes exhibited synergistic interphase formation mechanisms(CEI/SEI). Together, these interphases allowed stable coupling of agraphitic anode and a high-voltage cathode over an extended temperaturerange.

Unlike Examples 3-5 to 3-13, in Examples 3-1 through 3-4, 5 wt % or 10wt % polymer was introduced in the liquid electrolyte, formed polymersolid electrolytes. The gel polymer electrolyte exhibited propertiesbetween those of liquid and solid electrolytes in terms of the ionicconductivity and physical phase. From the test data in Table 3,liquid-level ionic conductivity was achieved if the physical integrityof polymer solid electrolytes was facilitated by using polymers.Problems such as electrolyte leakage and flammability could be mitigatedby using gel polymer electrolyte in electrochemical cells.

Unlike Comparison Example 3-1, in Examples 3-11 through 3-14, vinylenecarbonate (VC) or fluoroethylene carbonate (FEC) was introduced in theliquid electrolytes. Unlike

Examples 3-9 to 3-13, in Examples 3-5 to 3-8, VC or FEC was introducedin the polymer solid electrolytes. The introducing of additives, such asVC or FEC, could improve wetting process for battery manufacture andtesting. Some additives, such as VC or FEC, were able to preferentiallybreak down and undergo polymerization and ion-exchange reactions at theanode/electrolyte interface to produce SEIs with desirable chemicalcompositions and physical properties. For example, in a Li battery, astable SEI may be able to accommodate the cyclic volume changes at theanode during charge (addition) and discharge (removal) of metal atoms tothe electrode, which is good for stable long-term cell operation.

In summary, the introducing of flame retardant and/or sulfones appearedto considerably improve various electrochemical performances. Theseelectrolytes may help to achieve safe, long-life lithium secondarybatteries. The electrolytes in these experiments exhibited betteroxidation potential than the comparative materials, which suggests theymay be suitable for high voltage cathode materials. The improvedoxidation potential of the electrolytes can also provide enhancedstability in both liquid electrolytes and solid electrolytes, which mayprovide longer life and/or higher voltage lithium batteries. Inaddition, the electrolyte in these examples exhibited higher flashpoints and were highly stable at higher temperature, suggesting thatthey may be useful for high temperature lithium batteries as well asother applications. These properties may also benefit thecharging/discharging rate performances of lithium ion batteries.

EXAMPLE 4

The experiments described in this example use the procedures fromExamples 1 and 2, except modified as noted below.

Examples 4-1 to 4-4 provide testing information regarding to the saltconcentration. With increased amount of LiTFSI in dimethyl sulfone,assembled Li metal coin cells showed better cycling stability withcapacity retention improved from 60% to 65% at 200 cycles.

Example 4-5 to 4-10 provide the effectiveness of additives, includingethylene glycol and carbonate based derivatives.

Example 4-2 and 4-11 showed LiTFSI is a better salt than LiPF₆.

Example 4-12 and 4-13 provided alternative sulfone derivatives as iondissociation compound for Li metal battery.

Results are provided in Table 4. It was found that commercialelectrolytes had low electrochemical stability, and low cyclingstability towards the Li metal anode. In contrast, dimethylsulfone-based electrolytes provided higher oxidation potential, andbetter cycling performance in Li metal cells than commercialelectrolytes. Also, the addition of ethylene glycol provided bettercycling performance due to the decomposition of ethylene glycol andformed an SEI (solid electrolyte interphase). In some cases, theaddition of fluoroethylene carbonate may provide better cyclingperformance due to the decomposition of fluoroethylene carbonate and anSEI was formed. Also, the addition of trimethyl phosphate (a flameretardant) improved the safety of the battery.

The polymer used in Example 4-14 was as follows. It also included 40-60%of dimethyl sulfone and 30-50% of triethyl phosphate.

TABLE 4 Ion Capacity dissociation Oxidation Retention Ion compoundPotential (%) dissociation (Volume Additives Li salt vs. Li/Li+ (200cycle Example compound Percentage) Li salt (Volume Percentage)Concentration (V) 0.5 C) Example 4-1 Dimethyl 100% LiTFSI — 0.8M 5.5 V60% Example 4-2 Sulfone 100% LiTFSI — 1.0M 5.5 V 60% Example 4-3 100%LiTFSI — 1.2M 5.5 V 62% Example 4-4 100% LiTFSI — 1.8M 5.5 V 65% Example4-5  95% LiTFSI 1,2-dimethoxyethane 1.8M 5.1 V 74% (5%) Example 4-6  85%LiTFSI Tetraethylene Glycol 1.8M 5.2 V 81% dimethyl ether (15%) Example4-7  92% LiTFSI Fluoroehtylene Carbonate 1.8M 5.5 V 85% (8%) Example 60% LiTFSI Trimethyl Phosphate 1.8M 5.3 V 82% 4-8 (40%) Example  60%LiTFSI Triethyl Phosphate 1.8M 5.2 V 80% 4-9 (40%) Example  55% LiTFSITrimethyl Phosphate 1.8M 5.3 V 85% 4-10 (40%) Fluoroethylene Carbonate(5%) Example 100% LiPF6 — 1.0M 4.9 V 54% 4-11 Example 4-12 Diethyl 100%LiTFSI — 1.0M 5.2 V 52% Sulfone Example 4-13 Ethyl methyl 100% LiTFSI —1.0M 5.1 V 54% Sulfone Example 4-14 Dimethyl  55% LiTFSI TrimethylPhosphate 1.8M 5.0 V 80% Sulfone (40%) Fluoroethylene Carbonate (5%) 10wt % Polymer

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

In cases where the present specification and a document incorporated byreference include conflicting and/or inconsistent disclosure, thepresent specification shall control. If two or more documentsincorporated by reference include conflicting and/or inconsistentdisclosure with respect to each other, then the document having thelater effective date shall control.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.”

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc. When theword “about” is used herein in reference to a number, it should beunderstood that still another embodiment of the invention includes thatnumber not modified by the presence of the word “about.”

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

What is claimed is: 1-104. (canceled).
 105. A polymer solid electrolytesynthesized by crosslinking a mixture comprising a lithium salt, acrosslinkable monomer, a flame retardant as ion dissociation compound,and a carbonate additive that can enhance capacity retention of anelectrochemical device, wherein the crosslinkable monomer has a formulaof:

wherein the volume ratio of the additive to the ion dissociationcompound is between 5/95 and 50/50 and the polymer solid electrolyte hasan oxidation potential of at least 4.5 V with reference to Li/Li+. 106.The polymer solid electrolyte of claim 105, wherein the lithium salt isselected from the group consisting of LiTFSI, LiFSI, LiBOB, LiPF₆,LiBF₄, LiClO₄, LiAsF₆, LiN(CF₃SO₂)₂, LiC(CF₃SO₂)₃, LiDFOB, LiF, LiCl,LiBr, LiI, Li₂SO₄, LiNO₃, Li₃PO₄, Li₂CO₃, LiOH, lithium acetate, lithiumtrifluoromethyl acetate, and lithium oxalate.
 107. The polymer solidelectrolyte of claim 105, wherein the lithium salt has a concentrationranging from 0.5 M to 7 M in the mixture.
 108. The polymer solidelectrolyte of claim 105, wherein the carbonate additive is selectedfrom the group consisting of 1,2-dimethoxyethane carbonate, ethylenecarbonate (EC), vinylene carbonate (VC), fluoroethylene carbonate (FEC)and methylene ethylene carbonate.
 109. The polymer solid electrolyte ofclaim 105, wherein the flame retardant is a nitrogen-containing flameretardant, silicon-containing flame retardant, fluorine-containing flameretardant, an organophosphorus flame retardant or a combination thereof.110. The polymer solid electrolyte of claim 105, wherein the flameretardant is selected from the group consisting of methyldifluoroacetate, difluoroethyl acetate, trimethyl phosphate, triethylphosphate, and a mixture thereof.
 111. The polymer solid electrolyte ofclaim 105, wherein the crosslinkable monomer has a concentration rangingfrom 5 wt % to 40 wt % in the mixture.
 112. The polymer solidelectrolyte of claim 105, wherein the mixture for synthesizing thepolymer solid electrolyte comprises an initiator.
 113. The polymer solidelectrolyte of claim 112, wherein the initiator is selected from thegroup consisting of benzoyl peroxide, 2,2′-azobisisobutyronitrile(AIBN), 4,4-azobis(4-cyanovaleric acid) (ACVA), potassium persulfate,and ammonium persulfate.
 114. The electrochemical device of claim 105,wherein the mixture for synthesizing the polymer solid electrolytefurther comprises a phosphate additive.
 115. The electrochemical deviceof claim 114, wherein the phosphate additive is selected from the groupconsisting of trimethyl phosphate and triethyl phosphate.
 116. Anelectrochemical device comprising the polymer solid electrolyte of claim105.
 117. The electrochemical device of claim 116 further comprising ananode.
 118. The electrochemical device of claim 117, wherein the anodecomprises lithium metal.
 119. The electrochemical device of claim 117,wherein the anode comprises graphite.
 120. The electrochemical device ofclaim 116 further comprising a cathode.
 121. The electrochemical deviceof claim 120, wherein the cathode comprises an electroactive materialselected from the group consisting of lithium nickel cobalt manganeseoxide, lithium nickel cobalt aluminum oxide, lithium titanate, metalliclithium, lithium metal oxide, lithium manganese oxide, lithium cobaltoxide, and lithium iron phosphate.